1. Field of the Invention
Various aspects of the present invention relate to a suspension system linkage arrangement for an agricultural vehicle having a cab resiliently supported on the chassis of the vehicle.
2. Description of Related Art
The ride quality and operator comfort of a work vehicle is adversely affected by vibrations or movement transmitted from the frame or chassis of the vehicle to the operator's cab. As the cab typically is built separately from, and later mounted on, the frame, and because the cab is separate from the frame, movement of the frame may be transmitted through and amplified by the connections between the cab and the frame.
As the work vehicle travels across a surface, movement of the frame/chassis induces the operator's cab to pitch, roll and bounce. Movement of the cab can be particularly severe in agricultural and construction equipment vehicles (e.g., tractors, combines, backhoes, cranes, dozers, trenchers, skid-steer loaders, etc.), because such vehicles typically operate on off-road surfaces or fields having a high level of bumpiness.
Operator comfort may also be adversely affected by the operation of various systems on a work vehicle. In particular, operation of various work vehicle systems can cause forces to be applied to the chassis of the vehicle which, in turn, are transmitted to the cab. Examples of these forces include: draft forces exerted on the hitch of an agricultural tractor by an implement (e.g., a plow), which can cause the cab to pitch; normal forces applied to a work vehicle as the vehicle turns in response to a steering device, which can cause the cab to roll; clutch forces generated when a work vehicle clutch (e.g., a main drive clutch; four-wheel drive clutch) is engaged or disengaged, which can cause the cab to pitch; gear shift forces generated when a transmission of a work vehicle is shifted, which can cause the cab to pitch; braking forces generated as brakes of a work vehicle are operated, which can cause the cab to pitch; and acceleration forces generated when a speed actuator changes the speed of a work vehicle which can cause the cab to pitch.
The movement of the cab caused by surface bumps and the operation of vehicle systems cause both qualitative and quantitative problems. An operator of such a vehicle experiences increased levels of discomfort and fatigue caused by the vibrations. Productivity is decreased when an operator is forced to rest or shorten the work day, or is unable to efficiently control the work vehicle. The operator is also less likely to be satisfied with a work vehicle that provides poor ride quality. Under certain conditions, the frequency and magnitude of cab movement may force the operator to decrease driving speed, further decreasing productivity.
It is common for the cab, or operator station, to be mounted directly on the chassis and to rely only on springing in the operator's seat to improve operator comfort. This, however, is not entirely satisfactory, and therefore the cab can be supported on rubber mounts that provide an improved degree of cushioning.
Another known suspension system enables the cab to be resiliently mounted on the vehicle chassis. Stabilizer linkages are provided on the tractor fore and aft of the cab to limit the movement of the pivotal connection of the stabilizer linkages to the cab to essentially a vertical movement that lies in a vertical plane including the longitudinal centers of the vehicle chassis and the cab. A sway or yaw limiting mechanism as well as a pitch limiting mechanism are provided to limit the pitch and roll of the cab as it moves through the vertical plane relative to the vehicle chassis.
The present invention improves upon the known cab suspension systems, and thus it is to such a system that the present invention is primarily directed.